Suggest how blowing oxygen into molten cast iron removes most of the carbon

Carbon   is removed by  blowing oxygen into   the  molten  metal. it reacts with the carbon   producing  carbon   monoxide and  carbon  dioxide. these escape from the molten   metal. enough  oxygen   is used to achieve steel with the desired  carbon content .

Aphysical change is one that you can put in and remove like a ham sandwich. the stuff you put in there can be changem its not permanet. a chemical change is on that can't be change thats permanet. like when you make a cake and bake it. you can't get those ingredients back.